1. Technical Field
The field of art to which this invention pertains may be generally located in the class of devices relating to electromagnet and in particular to solenoid actuator which actuates mechanically a valve or piston or the like.
2. Background Information
As is known, the extremely widespread use of solenoids in many fields of electrical technology, automatic controls is due to the versatility of the numerous types provided. In particular, the trend of manufacturing of electrical devices, which currently use miniaturized electromagnetic apparatuses, is to reduce their dimensions and make them as compact as possible as well as more energy efficient.
In view of the above, solenoids manufacturers are therefore induced to manufacture solenoids that have smaller dimensions, especially in terms of length, and are increasingly sensitive, i.e, have a lower power consumption so as to reduce the dimensions of the power supply.
The problems encountered in the prior art solenoid is that the theoretical foundation guiding every area of their engineering is dated. The operation and limitations of electromagnetic devices and machinery based on the fundamental laws of electromagnetism, electromagnetic force relations, and all the limitations ascribed to the supposedly low permeability of magnetic materials, the excessive use of conducting wire(s), the relatively slow speed of action of the plunger and low magnetic efficacy resulting from the misconception that the available mechanical work is directly proportional to the bulk or weight of the magnet, which ignores the added effect tangential forces in the direction of the magnetic field intensity, the costly machining, fabricating and assembly methods required to improve efficacy, notwithstanding the high cost of high permeability ferromagnetic materials, all of which remain unsolved.
Previous efforts have been made in an attempt to increase the homogeneity of magnetic fields by devising new coils such as that of Gottfried J. Krueger, Reno di Leggiuno, Italy, U.S. Pat. No. 4,231,008, or by adding a permanent magnet circuit to the electromagnetic field as that of Tokie Uetsuhara, Urawa, Japan, U.S. Pat. No. 4,797,645, dated Jan. 10, 1989.
Whatever the precise merits, features and advantages of the above cited references, none of them achieves or fulfills the purposes of the current solenoid actuator.
3. Description of the Prior Art.
An example of a prior art electromagnetic solenoid actuator is described with reference to FIG. 1, which is one of the drawings indicated in the "brief description of the drawings" set forth later. The electromagnetic solenoid actuator of FIG. 1 comprises a magnetic circuit having a space energized by coil (11); a movable element (14) made of magnetic material which is inserted between pole face (12a) and (12b) of the stationary element (12) through a first gap (13), the movable element (14) can be mechanically moved in the direction represented by the arrow (14a) and (14b) moving with both the pole (12a) and (12b) at right angle, and a permanent magnet (16) fixed to a yoke (17) of the stationary element (12), the pole faces of the same polarity of the permanent magnet (16) are faced to the side surface of the movable element (14) through a small second gap (15).
In the electromagnetic solenoid actuator of FIG. 1, all the above mentioned demerits are present. Furthermore, the manufacturing process of combining a permanent magnet with an electromagnet is cumbersome. This type of solenoid actuator is designed on the basis of the misconception that the available mechanical work is directly proportional to the weight of the magnet and the magnetic efficacy can not be made greater than fifty percent.